一、标准库string类型
string类型支持长度可变的字符串,C++标准库将负责管理与存储字符相关的内存,以及提供各种有用的操作 ,在VC中直接F1查看
template <
class CharType,
class Traits=char_traits<CharType>,
class Allocator=allocator<CharType>
>
class basic_string
typedef basic_string<char> string; typedef basic_string<wchar_t> wstring;
要使用string类型对象,必须包含相关头文件
#include <string> using std::string;
string对象的定义和初始化:
string s1; //默认构造函数,s1为空串 string s2(s1); //将s2初始化为s1的一个副本 string s3(“value”); //将s3初始化为一个字符串字面值副本 string s4(n, ‘c’); //将s4初始化为字符‘c’的n个副本
常用成员函数:
例程1:
#include <string>
#include <iostream>
using namespace std;
int main(void)
{
string s1;
string s2("abcdefghijkl");
cout << s2 << endl;
basic_string<char> s3("xxx"); // 等价于string s3("xxx");
cout << s3 << endl;
string s4("abcdefg", 4);
cout << s4 << endl;
string s5(s2, 2, 3);
cout << s5 << endl;
string::iterator first = s2.begin() + 1;
string::iterator last = s2.begin() + 3;
string s6(first, last); //[first, last)
cout << s6 << endl;
return 0;
}
例程2:
#include <string>
#include <iostream>
using namespace std;
int main(void)
{
string s1("abcdefdg");
cout << s1.size() << endl;
cout << s1.length() << endl;
cout << s1.empty() << endl;
cout << s1.substr(1, 2) << endl;
cout << s1.substr(1) << endl; //等价于s1.substr(1, -1);
string::size_type pos = s1.find('d', 1);//位置从0开始算起
if (pos == string::npos) //npos = -1
cout << "not found" << endl;
else
cout << "pos=" << pos << endl;
pos = s1.rfind('d');
if (pos == string::npos)
cout << "not found" << endl;
else
cout << "pos=" << pos << endl;
return 0;
}
例程3:
#include <string>
#include <iostream>
using namespace std;
int main(void)
{
string s1("abcdefghijkl");
s1.replace(2, 2, "AAAAAA");
cout << s1 << endl;
s1 = "abcdefg";
s1.replace(s1.begin() + 1, s1.begin() + 4, "AAAAAA");
cout << s1 << endl;
string s2 = "xyzabc";
s2.insert(2, "MMMM"); //在位置2之前插入
cout << s2 << endl;
s2.append("6666");
cout << s2 << endl;
string s3 = "111";
s2.swap(s3);
cout << s2 << endl;
cout << s3 << endl;
return 0;
}
例程4:
#include <string>
#include <iostream>
using namespace std;
void fun(char *str)
{
cout << str << endl;
}
int main(void)
{
string s1 = "abc";
s1[1] = 'B';
cout << s1 << endl;
const string s2 = "xyz";
//s2[1] = 'Y'; Error s2[1] 返回的是 const char&
string s3 = "111" + s1 + "222" ;
cout << s3 << endl;
//s3.c_str()
fun(const_cast<char *>(s3.c_str()));
return 0;
}
例程5:
#include <string>
#include <iostream>
using namespace std;
int main()
{
string strinfo = " //*---Hello World!......------";
string strset = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
string::size_type first = strinfo.find_first_of(strset);
if(first == string::npos)
cout << "not find any characters" << endl;
string::size_type last = strinfo.find_last_of(strset);
if(last == string::npos)
cout << "not find any characters" << endl;
cout << strinfo.substr(first, last - first + 1) << endl;
return 0;
}
输出:Hello World
可以利用find_first_of 等操作去除空格,如去除左空格可以这样:
string s = " afas";
string drop = " \t";
s.erase(0, s.find_first_not_of(drop));
去除右空格:
string s = " dsfs ";
string drop = " \t";
s.erase(s.find_last_not_of(drop)+1);
参考:
C++ primer 第四版 Effective C++ 3rd C++编程规范